Recently, a phase change random access memory (“PRAM”) that stores information using a phase change film is getting attention as a high-speed, long life-spanned non-volatile memory element. The phase change film is formed of a material that, when heated to a high temperature (e.g. 600° C. or more) and then quickly cooled, is turned into an amorphous phase that exhibits a high resistivity, and, when heated to a low temperature (e.g. 400° C. or more) and cooled slowly, is turned into a crystalline phase that exhibits a normal resistivity. A PRAM stores data using difference in resistivity of these two phases. This phase change is achieved by controlling the magnitude of a current pulse. That is, when a large current pulse is provided, an amorphous phase is obtained and, when a small current pulse is provided, a crystalline phase is obtained.
As for a phase change film material used for PRAM, Ge2Se2Tes which is a Ge—Sb—Te film is used (see, e.g., Patent Document 1). As described in Patent Document 1, although the Ge—Sb—Te film has been generally formed by PVD such as, for example, sputtering, a step coverage is not sufficient with the PVD. Therefore, an attempt to form a film using CVD has been made which is excellent in step coverage.